This invention relates to fluid flow components; more particularly the invention relates to fluoropolymer couplings.
Numerous industries and many applications utilize metallic tubes, fittings, and various other xe2x80x9cplumbingxe2x80x9d components for handling and controlling critical fluid flow. Such components may be made of copper, stainless steel, and steel. Where the fluids being handled are under significant pressure or where containment integrity is critical, seals such as O-rings and flexible flat gaskets are typically utilized.
In particular applications such as semiconductor processing, the fluids involved react with and/or may be contaminated by the use of metallic components and conventional gaskets and elastomeric O-rings. Thus, in such industries, plumbing components are made of highly inert materials such as fluoropolymers, i.e., PFA and PTFE, for wetted components. In such applications, elastomeric O-rings are typically formed of two materials with a first traditional elastomeric material, such as silicon, encapsulated in a fluoropolymer coating. These O-rings are expensive and are subject to degradation and are typically considered to be single use.
Various fluoropolymer-based fittings and couplings have evolved for making connections between fluoropolymer components that do not utilize O-rings. Referring to Prior Art FIG. 1, one typical type of fitting is known in the industry as a FLARETEK(copyright) fitting. FLARETEK is a registered trademark of Fluoroware, Inc., the assignee of this patent application. In such a fitting 30 the elongate tapered nose section 32 with a threaded neck 34 engages within a tubular end portion 36 which is flared to fit over the tapered nose section. The flared section 38 will have a inside cylindrical surface 40 that has an inside diameter sized for the outside diameter of an outside cylindrical surface 42 of the nose section 32. The nose section thus xe2x80x9ctelescopesxe2x80x9d into the flared section 38. A nut 44 tightens the flared section onto the nose creating a seal 46 between the fitting body and the flared portion of the tubing portion. The flared end of the tubing is generally formed by heating the tubing and shaping the heated malleable tubing end into the desired flared configuration using steel forms.
Various other types of fluoropolymer fittings are known in the art. Some utilize separate gripper portions or internal ferrules. See for example U.S. Pat. Nos. 3,977,708 and 4,848,802. For connections between fluoropolymer valves and components such as fluoropolymer manifolds, sealing integrity between the components is typically accomplished by gaskets or fluoropolymer covered O-rings. In certain instances annular tongue-in-groove connections without O-rings or gaskets have been successfully utilized. These connections have the disadvantage that they must be precisely machined, i.e., tolerances of 0.0005 inches, and it can be difficult to properly align the mating pieces. Moreover, such connections are vulnerable to nicks and scratches which can compromise the integrity of the connection. Such a tongue-in-groove fitting is illustrated by U.S. Pat. No. 5,645,301. U.S. Pat. Nos. 3,977,708, 4,848,802, and 5,645,301 are incorporated herein by reference.
A coupling ideally suited for sealing between components such as a fluoropolymer valve body and a fluoropolymer manifold or for coupling tubing end portions, utilizes structure on said components for defining the sealing surfaces.
In a preferred embodiment, the coupling comprises a male protruding portion, also referred to as the nose a recessed female receiving portion, and a clamping means. The clamping means has an inner threaded surface for engaging a correspondingly threaded portion of the male protruding portion. The male protruding portion is shaped, generally, as a converging rounded conical frustum having an exterior surface, a primary sealing surface, a first stop surface, a second cooperating stop surface, and a fluid flow duct. The fluid flow duct is preferably concentrically positioned.
The recessed portion has a circular perimeter, an inwardly projecting annular ring, a first cooperating stop surface, a second stop surface, and a fluid flow duct. The fluid flow duct of the recessed portion is configured to cooperate with the fluid flow duct of the male protruding portion in order to form a continuous bore for the flow of fluid. The male protruding portion forms a seal by confronting the primary sealing surface and the annular sealing ring.
An advantage and feature of particular embodiments of the invention is that the male protruding portion is more easily manufactured with tolerances less critical than other known component-to-component sealing systems.
A further advantage and feature of particular embodiments of the invention is that the sealing components are self-centering, thereby facilitating assembly.
A further advantage and feature of the invention is that the base-to-base contact provides a positive stop such that additional torquing of screws does not impact the sealing characteristics of the sealing portions. Moreover, the optimum compression of the annular ring may be set at the contact of the stop surfaces.
A further advantage and feature of the invention is that the loading of the sealing surfaces is at an angle offset from engagement direction. This lessens the credibility of the compression between the components for an effective seal.